晋陕宁黄土丘陵区生态修复与农林牧业持续发展仿真研究

晋陕宁黄土丘陵区土壤侵蚀严重,生态环境脆弱,不合理利用土地是其主要原因,生态修复与环境重建是该区生态与经济持续发展的重要战略措施。应用系统动力学（System Dynamic,简称SD）和“反馈控制（Feedback control）理论建立了该区生态修复和环境重建的SD模型,它分为人口、农业、林业、牧业、农村经济、土壤侵蚀和生态环境6个模块,仿真时间1990～2080年,步长1a。经检验该SD模型的有效性为93．5％,可用于未来仿真预测。根据该区的生态环境特点和农牧业发展现状,选择生态环境恢复重建的3种典型模式——同步发展模式（A模式）、逐步调整模式（B模式）和现状发展模式（C模式）进行仿真研究,预测3种模式2000～2080年的土壤侵蚀、土地利用的发展动态以及农林牧业和生态环境演化趋势。仿真结果表明：土地利用与农、林、牧业持续发展密切相关,坡耕地和草场退化是制约农林牧业发展的主要因素。合理调整土地利用结构和加速治理侵蚀,可促进生态环境逐步恢复和农林牧业持续发展。同步发展模式（A模式）是该区生态修复和环境重建的3个仿真模式中的最优策略,它可促进农林牧协调发展和生态一经济趋向良性循环,并提出该区生态修复与环境重建的对策措施。该SD模型结构合理,运行功能良好,能较真实的模拟具有多变量、非线性变量的复杂生态系统的动态行为,为生态修复研究提供一种有效工具。     

红壤丘陵区土地利用方式变更后土壤有机碳动态变化的模拟

采用双组分模型模拟土地利用方式变更后土壤有机碳储量的变化,并用一些调查和监测数据进行了初步验证．此双组分模型将土壤有机碳分为新形成有机碳和原有有机碳两个组分．每个组分有机碳的形成转化用一级动力学方程描述．本文用此模型对亚热带土壤开垦利用为马尾松林地、湿地松林地、柑桔园和牧草地４种方式１０年来土壤有机碳储量的变化过程进行了模拟,初步结果表明,模拟值与实测值拟合较好．可见,此方法适于用来模拟不同土壤类型下土地利用系统变更初期的土壤有机碳储量动态变化过程．     

辽东湾滨海湿地景观规划预案分析与评价

在通过LEDESS模型对辽河三角洲景观规划预案所导致的生态后果进行模拟的基础上,通过构建综合反映区域生态经济效应的斑块生态经济指数,以GIS为工具,对各预案可能导致的区域生态经济效应进行了空间分析,并与现状进行了对比。结果表明,预案A（生境调整）和预案B（生境管理）不仅能够显著改善水禽生境,带来较高的生态效益,而且使区域综合的区域生态经济效益都有显著改善。预案C（农业开发）尽管能带来较高的经济效益,但由于导致的生境损失,其综合的生态经济效益与现状相比还有所下降。另外,模拟结果还表明,无破碎化的芦苇沼泽是生态经济综合效益最高的一类生境类型,是辽河三角洲滨海湿地生态经济最好的契合点。最后,在区域生态经济效应分析的基础上,对各景观规划预案进行了总体评价。     

GIS支持下的土地利用与土壤侵蚀强度相关性研究--以陕北黄土高原为例

依托GIS软件作为技术平台,采用网格地图与数学分析方法,研究了陕北黄土高原土地利用强度与土壤侵蚀强度之间的相互关系。结果表明,陕北黄土高原土壤侵蚀强度和土地利用强度呈高度正相关,说明土地利用强度是导致陕北黄土高原本区域土壤侵蚀的重要驱动力。回归分析发现,在自然因子综合作用下,土地利用强度对土壤侵蚀强度的影响呈现不同状况,地势越平坦、气候越湿润的地区人类活动对土壤侵蚀强度的影响越小,反之亦然。     

Effects of Landscape and Riparian Condition on a Fish Index of Biotic Integrity in a Large Southeastern Brazil River

Environmental conditions of a large river in southeastern Brazil were assessed by evaluating fish assemblage structure (index of biotic integrity, IBI), landscape use (forest, pasture, urban area, and tributary water) and riparian condition. A survey of the 338 km-long middle reach of the Rio Paraiba do Sul, containing a large urban-industrial complex, was conducted in two seasons: summer/wet and winter/dry. Fish were sampled with a standardized level of effort twice at seven sites, between March 2001 and April 2002, by gill nets, cast nets, sieves and seines. Riparian condition was evaluated by direct observations, and land use maps were used to assess landscape condition of an 8 km² buffer surrounding each site. IBI scores ranged from 5 to 36 (out of a possible range of 4–40), with lowest values at an urban-industrial landscape, and highest scores upstream and downstream, indicating the river’s recovery capacity. The most appropriate time to assess IBI was during the winter/dry period, when sampling was more effective and the IBI was more sensitive to changes in environmental quality. Landscape use and riparian condition were correlated, and IBI was positively correlated with % pasture, % tributary area, and riparian condition, but negatively correlated with % urban area. In some cases urban areas eliminated riparian woody vegetation, destabilizing site physical habitat structure.     

资源型城市土地利用变化的景观过程响应——以黑龙江省大庆市为例

土地利用与土地覆盖变化直接或间接地改变着景观生态系统的结构和功能,进而影响地表各种景观过程。地表景观过程的改变,必然对人类赖以生存的生态环境产生程度不同的影响。黑龙江省大庆市作为典型的资源型城市(以石油、草场和耕地资源发展起来),是人地关系作用最强烈的区域之一,也是土地利用发生急剧变化且具有特色的区域。揭示该区域土地利用的时空变化特征和变化规律,探讨土地利用变化的景观生态趋势及对生态环境的可能影响等,对于资源型城市生态环境改善,产业结构调整及实现资源型城市可持续发展尤为重要。为此,基于大庆市1978,1988,1992,1996,2001年5个时段的MSS和TM影像,获取20余年不同时期的土地利用信息,以GIS技术为数据集成分析平台,计算土地利用转移概率矩阵,景观格局指数和主要景观组分的转移过程贡献率,以期从景观格局的角度定量刻画区域景观过程对土地利用变化的响应。结果表明,区域内耕地不断增加,草地持续减少,建设用地和林地逐渐扩大,而湿地则一直大幅度减少;耕地和草地是区域的主要景观类型,但二者的景观动态及过程却不相同,耕地的景观过程表现为空间集中性加强,而草地的破碎化程度加强,景观组分间的转移过程频繁,景观不稳定;对维持当地生态系统稳定起重要作用的湿地景观,其破碎化过程最为明显且面积和平均斑块面积都在迅速减少,这种景观过程将对当地生态环境变化造成负面影响。草地退化,湿地萎缩和功能减退,沙化和盐碱化日趋严重等生态过程,是土地利用变化的景观生态过程响应,恢复与建设生态脆弱的资源型城市的景观生态系统,须对景观尺度上的土地利用方式进行合理的调控,而这一调控的有效途径在于政策、体制的调整和观念的变化。     

贵州喀斯特石漠化地区土地利用方式对土壤质量恢复能力的影响

喀斯特石漠化是一种与脆弱生态环境和人类活动相关联的土地退化过程,土地利用方式和人为生产经营活动方式及干扰程度对石漠化土壤质量的恢复和重建有明显影响。研究结果表明:林地、草地的有机质、全P和全K含量最高,分别是果树地和坡耕地的2.3、2.1、1.5倍和1.7、1.9、1.3倍,全氮量以草地最高,分别是其它利用方式的1.2~2.8倍,农地有机质含量仅次于林地和草地,石漠化地土壤营养元素最低。果树地和林地的微生物以细菌为主,分别占微生物总量的69.7%和73.3%,草地以固N菌为绝对优势,占微生物总数的33.0%,农地的放线菌多于草地、林地、果树地和坡耕地,石漠化地土壤微生物数量和多样性最低。经开垦利用后(坡耕地),喀斯特山区表层土壤颗粒砂化逐渐明显。石漠化区经过13a退耕还林后,植物多样性指数和均匀度分别由0.96和0.29提高了1.92和0.53,优势度由0.75降到0.36。采用合适的土地利用方式,辅于必要的生物措施,是恢复喀斯特石漠化地区土壤质量的有效途径之一。     

An integrated exploratory approach to examining the relationships of environmental stressors and fish responses

The Chesapeake Bay is one of the mostproductive systems in the world. It is theNation's largest estuary (64,000 square miles)and is home to about 13 million people. Itsupports a variety of aquatic resources offlora and fauna. However, for the past 350years and especially in the last two to threedecades, there has been substantialdeterioration of the natural resources. Manyspecies of submerged aquatic vegetation andbenthic invertebrates have been diminished orbecome extinct. Commercial harvests of fish,crab and shell fish have also declined.In 1983, a Chesapeake Bay Agreement was signedby Pennsylvania, Maryland, the District ofColumbia, Virginia and the Bay Commission. Itwas subsequently amended in 1987 and 1992. TheAgreement identified the improvement andmaintenance of water quality as the mostcritical elements in the overall restorationand protection of the Chesapeake Bay. In orderto restore the Bay area and to conserve thefish resources, the causal relationshipsbetween the environmental stressors and thecomposition and health of the fish communitiesmust be understood.Multivariate ordination techniques are usefulexploratory tools to help elucidate latentenvironmental relationships, define specificbiocriteria and to generate hypotheses. Geographical information systems (GIS) is ananalytical technique for identifying spatialrelationships. In this project, an integratedmethodology involving the use of multivariateordination, statistical, and GIS techniques wasadopted. A non-metric multi-dimensionalscaling (NMDS) ordination technique wasemployed in conjunction with other statisticaltechniques (such as correlation analysis) andArcView GIS to analyze a huge data set from theMaryland Biological Stream Survey (MBSS). Theobjectives were to elucidate the intricaterelationships between a suite of environmentalfactors and fish conditions in the riverinesystem in the Chesapeake Bay and to evaluatethe effectiveness of this approach inexploratory analyses.The results showed that landuse issignificantly related to nutrient loading. Toa large extent, landuse and nitrates are alsoaffecting the composition and health of thefish communities in some subwatersheds in theChesapeake Bay. It was also found that theapproach adopted in this study is flexible,requiring few model assumptions. But it iscomprehensive and reliable, capable ofrevealing the impacts of environmentalstressors on the ecology, structure,composition and health of the fishcommunities.     

Alien plant assemblages near roads in arid and semi-arid South Africa

Herbaceous and woody alien plants visible from a moving vehicle were recorded along 1 km roadside transects at 5 km intervals over a distance of 5869 km in the semi-arid and arid Fynbos, Succulent Karoo, Nama Karoo and Arid Savanna (Kalahari) biomes in South Africa. Each 1 km transect was classified by biome and vegetation type, mean annual rainfall, rainfall seasonality, soil surface type and landuse adjoining the roadside. Although travelling speed affected the range and frequency of plant species observed, the method was repeatable at a speed of 100 km h^?1. Alien plants occurred in 98% of 119 Fynbos, 81% of 204 Succulent Karoo, 72% of 661 Nama Karoo, 47% of 171 Arid Savanna and 100% of seventeen Grassland transects. Alien species richness per site was correlated with mean annual rainfall, but in all regions, sites adjacent to cultivation had significantly more alien species than sites adjoining rangeland. The alien plant assemblage of the arid winter-rainfall Succulent Karoo included species from mesic winter-rainfall lowland Fynbos and the arid Nama Karoo receives unseasonal rainfall. The frequencies of Prosopis spp., Atriplex spp. and Opuntia ficus-indica were not significantly greater near cultivation, and these perennial plants, all of which are dispersed by indigenous and domestic animals, can invade natural rangeland in arid and semi-arid southern Africa.     

Impact of land use changes on water resources and biodiversity of Lake Nakuru catchment basin, Kenya

Lake Nakuru, Kenya, is one of a series of saline–alkaline closed basin lakes in the eastern arm of the Rift Valley. The lake has been variously described as ' the lake of a million flamingos' and 'the Worlds greatest ornithological spectacle' and is bedrock to the areas' tourism. The lake was designated a bird sanctuary in 1960, a National Park in 1968, first rhino sanctuary in 1987, first Kenyan Ramsar site in 1990, an Important Bird Area in 1999 and a world-class national park in 2005. Over the last 40 years, its basin has been heavily settled, extensively cultivated, urbanized and industrialized. Environmental problems include poor agricultural practices, human encroachment, pollution, wildlife mortality/morbidity, human/wildlife conflicts, poverty, ethnic tensions and land clashes and lack of adequate legal and policy framework. Approaches to conservation have been initiated against identified existing problems and constraints. These approaches are (i) organizational and institutional development; (ii) hot spots and pollution loads management and (iii) catchment and park management. Constraints have been identified as unclear demarcation of responsibilities, lack of budget, skilled staff and know-how and lack of environmental standards and regulations. The impacts of ecosystem changes on people's lives and livelihoods are discussed.